The present invention relates to an aggregate for feeding a fuel from a supply tank to an internal combustion engine of a motor vehicle.
One of such aggregates is disclosed for example in U.S. Pat. No. 4,854,830. The feeding aggregate disclosed in this reference has an electric drive motor which rotates an impeller of a feeding pump formed as a flow pump. The disc-shaped impeller is provided on its periphery with a plurality of radially outwardly extending vanes and rotates in a cylindrical pump chamber limited in an axial direction of the impeller by two opposite end walls and in a radial direction by a ring wall. A partially ring-shaped groove extending around the rotary axis of the impeller is provided in the axial end walls of the pump chamber at the height of the vanes and forms with the impeller a feeding passage. The feeding passage extends from an inlet opening in the pump chamber at its one end to an outlet opening at its another end. During the rotary movement of the impeller fuel is aspirated into the pump chamber through the inlet opening and discharged with increased pressure through the outlet opening.
The known aggregate is provided with recesses in the axial end walls of the impeller for avoiding an increased wear and a high noise generation due to inclination of the impeller and a wall contact caused by asymmetrical pressure forces resulting from a very narrow axial gap between the impeller and the end walls of the pump chamber. During the rotary movement of the impeller the recesses are filled with fuel so that a hydraulic buffer is provided between the impeller and the axial walls of the pump chamber.
While the recesses in the known feeding aggregate can be designed in different ways, they are always limited by their location in the axial end faces of the impeller. This has however the disadvantage that the hydraulic buffer is limited to the region arranged radially inwardly of the feeding passage. The axial pressure forces act however at the height of the feeding passage on the impeller and can generate, due to the great distance from the impeller axis (lever action) relative to the hydraulic buffer, great resulting forces. Therefore the formation of the hydraulic buffer in the known feeding aggregate does not reliably eliminate the inclined positions of the impeller.